The effect of sporulation temperature on sporal characteristics of Bacillus subtilis A

Spores of Bacillus subtilis A were produced at different temperatures (23 degree -49 degree C) and examined for a number of sporal characteristics. Spore heat resistance increased with sporulation temperature to 45 degree C, with spores grown at 49 degree C showing a dramatic reduction in resistance. Spore crops showed biphasic thermal death curves whether enumerated on germination medium with or without calcium dipicolinate. There appeared to be no direct correlation with sporulation temperature, heat resistance, and dipicolinate content. There was an increase in both the magnesium and calcium contents to 45 degree C with a dramatic reduction at 49 degree C. The 1.305 density spores had higher calcium and dipicolinate contents than the 1.275 spores, although both spore types showed biphasic thermal death curves. The mechanisms involved in determining which spore type is produced at a specific growth temperature is unknown.